scholarly journals A subadult individual of Styracosaurus albertensis (Ornithischia: Ceratopsidae) with comments on ontogeny and intraspecific variation in Styracosaurus and Centrosaurus.

2020 ◽  
Vol 8 ◽  
pp. 67-95 ◽  
Author(s):  
Caleb Brown ◽  
Robert Holmes ◽  
Phillip Currie
Keyword(s):  
Intraspecific Variation ◽  
Maximum Size ◽  
Early Ontogeny ◽  
Adult Size ◽  
Immature Individual ◽  
Cranial Ontogeny ◽  
Position And Orientation ◽  
Large Spike ◽  
Large Adult ◽  
Size Series

Styracosaurus albertensis is an iconic centrosaurine horned dinosaur from the Campanian of Alberta, Canada, known for its large spike-like parietal processes. Although described over 100 years ago, subsequent discoveries were rare the last few decades, during which time several new skulls, skeletons, and bonebeds were found. Here we described an immature individual, the smallest known for the species, represented by a complete skull and fragmentary skeleton.  Although ~80% maximum size, it possesses a suite of characters associated with immaturity, and is regarded as a subadult.  The ornamentation is characterized by a small, recurved, but fused nasal horncore; low, rounded postorbital horncores; and short, triangular, and flat parietal processes. Using this specimen, and additional skulls and bonebed material, the cranial ontogeny of Styracosaurus is described, and compared to Centrosaurus.  Styracosaurus shows a similar early ontogeny of the nasal horncore, starting thin, recurved, and unfused, but retains the recurved morphology into large adult size, and never develops the procurved morphology common in Centrosaurus. The postorbital horncores of Styracosaurus are lower and more rounded than those of Centrosaurus throughout ontogeny, and show greater resorption later in ontogeney. The length and thickness of the parietal processes increase drastically through ontogeny, but their position and orientation are static across the size series. Several diagnostic Styracosaurus albertensis specimens now preserve medially orientated P3 spikes, causing issues for the diagnosis of S. ovatus. Variability in parietal ornamentation, either expression of P1 and P2 parietal processes, or other cranial ornamentations, does not appear to correlate with stratigraphy.

Persistence of giants: population dynamics of the limpet Scutellastra laticostata on rocky shores in Western Australia

2020 ◽  
Vol 646 ◽  
pp. 79-92
Author(s):  
RE Scheibling ◽  
R Black
Keyword(s):  
Population Dynamics ◽  
Western Australia ◽  
Size Structure ◽  
Survival Rates ◽  
Maximum Size ◽  
High Rate ◽  
Adult Survival ◽  
Rocky Shores ◽  
Adult Size ◽  
Decadal Time Scale

Population dynamics and life history traits of the ‘giant’ limpet Scutellastra laticostata on intertidal limestone platforms at Rottnest Island, Western Australia, were recorded by interannual (January/February) monitoring of limpet density and size structure, and relocation of marked individuals, at 3 locations over periods of 13-16 yr between 1993 and 2020. Limpet densities ranged from 4 to 9 ind. m-2 on wave-swept seaward margins of platforms at 2 locations and on a rocky notch at the landward margin of the platform at a third. Juvenile recruits (25-55 mm shell length) were present each year, usually at low densities (<1 m-2), but localized pulses of recruitment occurred in some years. Annual survival rates of marked limpets varied among sites and cohorts, ranging from 0.42 yr-1 at the notch to 0.79 and 0.87 yr-1 on the platforms. A mass mortality of limpets on the platforms occurred in 2003, likely mediated by thermal stress during daytime low tides, coincident with high air temperatures and calm seas. Juveniles grew rapidly to adult size within 2 yr. Asymptotic size (L∞, von Bertalanffy growth model) ranged from 89 to 97 mm, and maximum size from 100 to 113 mm, on platforms. Growth rate and maximum size were lower on the notch. Our empirical observations and simulation models suggest that these populations are relatively stable on a decadal time scale. The frequency and magnitude of recruitment pulses and high rate of adult survival provide considerable inertia, enabling persistence of these populations in the face of sporadic climatic extremes.

scholarly journals Ngwevu intloko: a new early sauropodomorph dinosaur from the Lower Jurassic Elliot Formation of South Africa and comments on cranial ontogeny in Massospondylus carinatus

PeerJ ◽  
2019 ◽  
Vol 7 ◽  
pp. e7240 ◽  
Author(s):  
Kimberley E.J. Chapelle ◽  
Paul M. Barrett ◽  
Jennifer Botha ◽  
Jonah N. Choiniere
Keyword(s):  
South Africa ◽  
New Species ◽  
Sexual Dimorphism ◽  
New Genus ◽  
Lower Jurassic ◽  
Early Jurassic ◽  
Adult Size ◽  
Minimum Age ◽  
Cranial Ontogeny ◽  
Morphological Differences

Our knowledge of Early Jurassic palaeobiodiversity in the upper Elliot Formation of South Africa has increased markedly in recent years with the discovery of new fossils, re-assessments of previously collected material and a better understanding of Stormberg Group stratigraphy. Here, Ngwevu intloko, a new genus of upper Elliot basal sauropodomorph is named on the basis of a complete skull and partial skeleton (BP/1/4779) previously assigned to Massospondylus carinatus. It can be distinguished from all other basal sauropodomorphs by a combination of 16 cranial and six postcranial characters. The new species is compared to a small ontogenetic series of M. carinatus as well as to a range of closely related taxa. Taphonomic deformation, sexual dimorphism and ontogeny are rejected as possible explanations for the morphological differences present between BP/1/4779 and other taxa. Osteohistological examination reveals that BP/1/4779 had nearly reached adult size at the time of its death at a minimum age of 10 years.

scholarly journals Osteohistology of Late Triassic prozostrodontian cynodonts from Brazil

PeerJ ◽  
2018 ◽  
Vol 6 ◽  
pp. e5029 ◽  
Author(s):  
Jennifer Botha-Brink ◽  
Marina Bento Soares ◽  
Agustín G. Martinelli
Keyword(s):  
Bone Tissue ◽  
Life Histories ◽  
Small Body ◽  
Growth Period ◽  
Early Ontogeny ◽  
Growth Patterns ◽  
Late Triassic ◽  
Adult Size ◽  
Body Sizes ◽  
One Year

The Prozostrodontia includes a group of Late Triassic-Early Cretaceous eucynodonts plus the clade Mammaliaformes, in which Mammalia is nested. Analysing their growth patterns is thus important for understanding the evolution of mammalian life histories. Obtaining material for osteohistological analysis is difficult due to the rare and delicate nature of most of the prozostrodontian taxa, much of which comprises mostly of crania or sometimes even only teeth. Here we present a rare opportunity to observe the osteohistology of several postcranial elements of the basal prozostrodontid Prozostrodon brasiliensis, the tritheledontid Irajatherium hernandezi, and the brasilodontids Brasilodon quadrangularis and Brasilitherium riograndensis from the Late Triassic of Brazil (Santa Maria Supersequence). Prozostrodon and Irajatherium reveal similar growth patterns of rapid early growth with annual interruptions later in ontogeny. These interruptions are associated with wide zones of slow growing bone tissue. Brasilodon and Brasilitherium exhibit a mixture of woven-fibered bone tissue and slower growing parallel-fibered and lamellar bone. The slower growing bone tissues are present even during early ontogeny. The relatively slower growth in Brasilodon and Brasilitherium may be related to their small body size compared to Prozostrodon and Irajatherium. These brasilodontids also exhibit osteohistological similarities with the Late Triassic/Early Jurassic mammaliaform Morganucodon and the Late Cretaceous multituberculate mammals Kryptobaatar and Nemegtbaatar. This may be due to similar small body sizes, but may also reflect their close phylogenetic affinities as Brasilodon and Brasilitherium are the closest relatives to Mammaliaformes. However, when compared with similar-sized extant placental mammals, they may have grown more slowly to adult size as their osteohistology shows it took more than one year for growth to attenuate. Thus, although they exhibit rapid juvenile growth, the small derived, brasilodontid prozostrodontians still exhibit an extended growth period compared to similar-sized extant mammals.

Early ontogeny of seedlings of Pinus radiata

1972 ◽  
Vol 50 (11) ◽  
pp. 2381-2387 ◽  
Author(s):  
Richard T. Riding
Keyword(s):  
Seed Coat ◽  
Pinus Radiata ◽  
Low Frequency ◽  
Maximum Size ◽  
Early Ontogeny ◽  
Axillary Bud ◽  
Minimum Size ◽  
Storage Products ◽  
Bud Initiation ◽  
Needle Primordia

The pattern of branching in seedlings of Pinus radiata appeared to be correlated with the size and zonation of the shoot apex. Just before splitting of the seed coat, the apex reached a maximum size and granular storage products, present in the embryo, were no longer evident. Shortly after the seed coat split, the hypocotyl and cotyledons became green. The first needle primordia were formed alternate to the cotyledons. Zonation of the apex was evident at this time; however, the apical zone was homogeneous and cells of the pith–rib-meristem had not elongated. Buds were initiated in the axils of many of the first-formed needle primordia. Needle initiation progressed rapidly up the flanks of the apex, reducing it to a minimum size shortly after the cotyledons emerged from the seed coat. Nodes formed at this time had a low frequency of axillary bud formation. During early epicotyl elongation the rate of needle initiation decreased and cell divisions were evident throughout the apex. The apex then increased in size and developed a zonation similar to that found in mature plants. As the apex increased in size, the frequency of axillary bud initiation also increased.

The world's biggest trilobite—Isotelus rex new species from the upper Ordovician of northern Manitoba, Canada

2003 ◽  
Vol 77 (1) ◽  
pp. 99-112 ◽  
Author(s):  
David M. Rudkin ◽  
Graham A. Young ◽  
Robert J. Elias ◽  
Edward P. Dobrzanski
Keyword(s):  
New Species ◽  
Rapid Onset ◽  
Adult Size ◽  
Upper Ordovician ◽  
Low Latitude ◽  
Large Size ◽  
Extinction Event ◽  
Widespread Phenomenon ◽  
Climatic Cooling ◽  
Large Adult

The largest known trilobite fossil, a virtually complete articulated dorsal shield of the asaphid Isotelus rex new species, has been recovered from Upper Ordovician (Cincinnatian, Richmondian) nearshore carbonates of the Churchill River Group in northern Manitoba. At over 700 mm in length, it is almost 70 percent longer than the largest previously documented complete trilobite, and provides the first unequivocal evidence of maximum trilobite length in excess of one-half metre. Comparisons with other fossil and extant members of the phylum suggest that in terms of maximum linear dimensions it was among the biggest arthropods ever to have lived. Sediments of the Churchill River Group were deposited in an equatorial epeiric setting and the extremely large size of I. rex n. sp. thus marks a striking example of low-latitude gigantism, in sharp contrast to the widespread phenomenon of “polar gigantism” in many modern marine benthic arthropods. Lack of extensive epibiontic colonization of the exoskeletal surface and the presence of large distinctive trace fossils in the same unit suggest that I. rex n. sp. may have been a semi-infaunal predator and scavenger that employed a shallow furrowing and probing mode of benthic feeding. The extinction of the isotelines (and virtually the entire asaphide lineage) at the end of the Ordovician cannot be related to the near contemporaneous achievement of exceptionally large adult size in some representatives. Failure to survive the terminal Ordovician extinction event was most likely a consequence of a pelagic larval life-style that proved ill-adapted to the rapid onset of global climatic cooling and loss of tropical shelf habitats.

EVOLUÇÃO DA ICTIOFAUNA DE RIACHOS SUL-AMERICANOS (CASTRO, 1999) REVISITADO APÓS MAIS DE DUAS DÉCADAS

2021 ◽  
Vol 25 (02) ◽  
pp. 231-245
Author(s):  
Ricardo Macedo Corrêa e Castro ◽  
Keyword(s):  
Maximum Size ◽  
Taxonomic Diversity ◽  
Respiratory Physiology ◽  
South American ◽  
Adult Size ◽  
The South ◽  
Evolutionary Pattern ◽  
The Family ◽  
Respective Species

A little more than 20 years after the first publication of Castro (1999), the knowledge of the South American freshwater ichthyofauna, especially that of Brazil, has increased dramatically. This increase occurred both in terms of knowledge of its taxonomic diversity - in 1999, based on various sources in the scientific literature, a total of 2,800 species of South American freshwater fish was estimated, and a total of near 3,500 species it is currently known from Brazil alone - as to the knowledge of its evolution and also ecology. Consequently, all the hypotheses originally proposed in that paper are reexamined and critically discussed here considering this new knowledge accumulated in the past nearly two decades. Although the original 1999 hypothesis that the small adult size of their respective species is a general evolutionary pattern shared by the South American stream ichthyofauna has been firmly corroborated by several studies carried out in many regions of Brazil, the different patterns associated with most of the species of stream fish originally proposed are discussed in this chapter in the light of the new accumulated knowledge about their biology and ecology. Likewise, the possible role of heterochrony in their respective evolution is critically analyzed in the context of the great advance that has occurred in understanding the phylogenetic relationships of component taxa of freshwater neotropical ichthyofauna, using mainly the family Characidae as a possible model. Finally, a recent intriguing idea of the role of respiratory physiology in determining both the maximum size of teleost fish and their patterns of environmental occupation is examined in relation to its possible effect in the evolution of South American stream ichthyofauna.

A new species of Plestiodon (Squamata: Scincidae) from Sierra Madre del Sur of Guerrero, México

Zootaxa ◽  
2012 ◽  
Vol 3339 (1) ◽  
pp. 57 ◽  
Author(s):  
MANUEL FERIA-ORTIZ ◽  
URI OMAR GARCÍA-VÁZQUEZ
Keyword(s):  
New Species ◽  
Lateral Line ◽  
Adult Size ◽  
Sierra Madre ◽  
Sierra Madre Del Sur ◽  
Large Adult ◽  
A New Species

We describe a new species of lizard of the genus Plestiodon from the Sierra Madre del Sur of Guerrero, Mexico. Plestiodonnietoi sp. nov. shares a characteristic with all members of the P. brevirostris group in that the scale that medially bordersthe postgenial is wider than long. This species is most similar to P. brevirostris and P. indubitus from which it differs byhaving the following combination of characters: large adult size, interparietal enclosed posteriorly by parietals, and a pale lateral line on the neck.

A new species of the genus Scutiger (Anura: Megophryidae) from southeastern Tibet, China

Zootaxa ◽  
2012 ◽  
Vol 3388 (1) ◽  
pp. 29 ◽  
Author(s):  
KE JIANG ◽  
DINGQI RAO ◽  
SIQI YUAN ◽  
JISHAN WANG ◽  
PIPENG LI ◽  
...  
Keyword(s):  
New Species ◽  
Breeding Season ◽  
Type Locality ◽  
Adult Size ◽  
Large Adult ◽  
A New Species ◽  
Southeastern Tibet

A new species of Scutiger Theobald, 1868 is described from Medog, southeastern Tibet, China. Scutiger wuguanfui sp.nov. is distinguished from congeners in the following combination of characters: (1) large adult size, female is much largerthan male; (2) maxillary teeth absent; (3) male with a pair of pectoral glands and a pair of axillary glands, axillary glandssimilar to pectoral glands, all of them covered by black spines in breeding season; (4) in breeding male, nuptial spines ondorsal surface of firs and second fingers, and inner side of third finger; (5) male with an internal single subgular vocal sac,a pair of slit-like openings of vocal sac near corners of the mouth. This new species is currently known only from the type locality.

An Experiment with Medaka, Oryzias latipes, and a Critique of the Hypothesis that Teleost Egg Size Controls Vertebral Count

1971 ◽  
Vol 28 (9) ◽  
pp. 1235-1240 ◽  
Author(s):  
C. C. Lindsey ◽  
M. Y. Ali
Keyword(s):  
Related Species ◽  
Egg Size ◽  
Oryzias Latipes ◽  
Causal Connection ◽  
Adult Size ◽  
Vertebral Number ◽  
Vertebral Count ◽  
Large Adult

In each of two sets of experiments, two female medaka, Oryzias latipes, that laid different-size eggs were crossed reciprocally with two males. Vertebral counts of the offspring differed significantly between batches, but there was no consistent correlation between egg size and vertebral count. Both the highest and lowest counts resulted from crosses with females laying large eggs. Other experiments are reviewed, and it is concluded that within the same race of fish there is no causal connection between vertebral number and egg size, although between different races or related species large adult size is often correlated with high vertebral count. The possible advantages of variation in vertebral number are discussed.

Observations on Astiericeras astierianum (d'Orbigny, 1842) (Cretaceous Ammonoidea)

1986 ◽  
Vol 123 (5) ◽  
pp. 507-513 ◽  
Author(s):  
W. J. Kennedy
Keyword(s):  
Intraspecific Variation ◽  
Early Ontogeny ◽  
Type Material ◽  
The Family ◽  
First Time ◽  
Derivatives Of

AbstractAstiericeras astierianum (d'orbigny, 1842) is redescribed, the type material illustrated for the first time and the range of intraspecific variation and striking sexualdimorphism documented. Previous suggestions that the early ontogeny of Astiericeras supports derivation from Douvilleiceras de Grossouvre, 1894 of the Douvilleiceratinae are in error: the genus and species are distinctive at the earliest diameters seen and ornament gives no clue to affinities. The sutural formula is that characteristic of some Douvilleicerataceae, however, to which superfamily the species is assigned, as the only member of the family Astiericeratidae Breistroffer, 1953. It is thus a scaphitoid heteromorph, derived from normally coiled immediate ancestors that are themselves recoiled derivatives of an original heteromorphic stock.

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